IS 3400 (Part 23): ISO 7619:1997 2002 (Reaffirmed - 2012) Indian Standard METHODS OF TEST FOR VULCANIZED RUBBERS PART 23: RUBBER -- DETERMINATION OF INDENTATION HARDNESS BY MEANS OF POCKET HARDNESS METERS ICS 83.060 @ BIS 2002 BUREAU MANAK BHAVAN, OF 9 IN NEW DIANSTA SHAH 110002 DELHI ND ZAFAR ARDS MARG BAHADUR July 2002 Price Group 5 Rubber Products Sectional Committee, PCD 13 NATIONAL FOREWORD This Indian Standard (Part 23) which is identical with ISO 7619:1997 `Rubber -- Determination of indentation hardness by means of pocket hardness meters' issued by the International Organization for Standardization (ISO) was adopted by the Bureau of Indian Standards on the recommendations of the Rubber Products Sectional Committee and approval of the Petroleum, Coal and Related Products Division Council. The text of ISO Standard has been proposed to be approved Standard without deviations. Certain conventions are, however, Standards. Attention is particularly drawn to the following: a) Wherever the words `International read as `Indian Standard'. Standard' appear as suitable for publication as Indian not identical to those used in Indian referring to this standard, they should be b) Comma (,) has been used as a decimal marker while in Indian Standards, is to use a point (.) as the decimal marker. the current practice In this adopted standard, reference appears to certain International Standards for which Indian Standards also exist. The corresponding Indian Standards which are to be substituted in their place are listed below along with their degree of equivalence for the editions indicated. However, that International standard cross-referred in this adopted ISO Standard which has subsequently been revised, position in respect of latest ISO Standard has been given. International Standard ISO 48:1994 Rubber, vulcanised thermoplastic -- Determination hardness (hardness between IRHD and 100 IRHD) or of 10 Corresponding Indian Standard IS 3400 (Part 2) :1995 for vulcanized rubbers: Methods of test Part 2 Hardness Degree of Equivalence Technically equivalent with minor deviation (second revision) IS 13867:1993 Rubber standard temperatures, humidities and times for and time interval the conditioning between vulcanization and testing of test pieces temperature and the relative humidity 1s0 471:1995 Rubber -- Temperatures, humidities and times for conditioning and testing do For tropical countries like India, the standard 27 ~ 2°C and 65 * 5 percent respectively. shall be taken as In reporting the results of a test or analysis made in accordance with this standard, if the final value, observed or calculated, is to be rounded off, it shall be done in accordance with IS 2:1960 `Rules for rounding off numerical values (revised)'. IS 3400 ( Part 23 ) :2002 ISO 7619: 1997 Indian Standard METHODS OF TEST FOR VULCANIZED RUBBERS PART 23 RUBBER -- DETERMINATION OF INDENTATION HARDNESS BY MEANS OF POCKET HARDNESS METERS WARNING -- Persons using this International Standard should be familiar with normal laboratory practice. This standard does not purport to address all of the safety problems, if any, associated with its use. It is the responsibility of the user to establish appropriate safety and health practices and to ensure compliance with any national regulatory conditions. 1 Scope of the indentation hardness of rubber by 1.1 This International Standard specifies a method for the determination means of pocket hardness meters of two types: a) b) the Shore-type durometer; in IRHD. a meter calibrated Two types of Shore-type durometer are described; durometer range and type D for rubbers in the high hardness range. type A is used for rubbers in the normal hardness 1.2 The use of pocket meters is primarily intended for control purposes and is not recommended for specification purposes. For such purposes, the methods given in ISO 48 should be used. It is possible to increase the precision by fixing the pocket hardness tester on a support. 1.3 A similar method for measuring the hardness of plastics is given in ISO 868:1985, Determination of indentation hardness by means of a durometer (Shore hardness). P/astics and ebonite -- NOTE 1 The hardness of rubber, as measured by the Shore A durometer or the IRHD meter, is not a simple fundamental property but is a complex response to an applied indentation. The measurement will depend upon the following factors: a) b) c) d) e) f) 9) the elastic modulus of the rubber; the viscoelastic the thickness the geometry properties of the rubber; of the test piece; of the indento~ the pressure exerted; the rate of increase of pressure; the interval at which the hardness is recorded, directly to IRHD values, although Because of these factors, results using a Shore A durometer should not be related correlations have been established for some individual rubbers or compounds. 1 IS 3400 ( Part 23 ) :2002 ISO 7619: 1997 2 Normative references The following standards contain provisions which, through reference in this text, constitute provisions of this International Standard. At the time of publication, the editions indicated were valid. All standards are subject to revision, and parties to agreements based on this International Standard are encouraged to investigate the possibility of applying the most recent editions of the standards indicated below. Members of IEC and ISO maintain registers of currently valid International Standards. ISO 48:1994, 100 IRHD). ISO 471:1995, Rubber -- Times, temperatures and humidities for conditioning and testing. Rubber, vulcanized or thermoplastic -- Determmat/on of hardness (hardness between 10 IRHD and 3 Principle property is the penetration of a specified indentor forced into the material under specified conditions. The measured 4 4.1 Apparatus Shore-type durometers: Types A and D described in 4.1.1 to 4.1.4, The durometers consist of the components 4.1.1 Pressure foot, with a central hole of diameter between 2,5 mm and 3,2 mm, centred at least 6 mm from any edge of the foot. 4.1.2 Indenter, formed from a hardened steel rod of 1,25 mm* 0,15 mm diameter shown in figure 1, for type A durometers, and figure 2 for type D durometers. to the shape and dimension 4.1.3 Indicating device, allowing the extent of protrusion of the point of the indentor beyond the face of the pressure foot to be read off; the device shall be calibrated directly in terms of units ranging from O, for the maximum protrusion of 2,50 mm * 0,04 mm, to 100 for nil protrusion obtained by placing the pressure foot and indentor in firm contact with a flat piece of glass. 4.1.4 a) Calibrated F=550+75HA where F HA b) is the applied force, in millinewtons; is the hardness reading on the type A durometer. spring, to apply force to the indentor in accordance with one of the following equations: F = 445 H~ where F HD is the applied force, in millinewtons; k the hardness reading on the type D durometer. 2 IS 3400 ( Part 23 ) :2002 ISO 7619: 1997 Dimensions in millimetres +0,2 m 00,79*0,03 I I Figure 1 -- Indenter for type A durometer Dimensions in millimetres +0,2 03-0,5 m Figure 2 -- Indenter for type D durometer 3 IS ISO 3400 7619: ( Part 23 ) :2002 1997 4.2 The The IRHD pocket hardness meter calibrated in IRHD consists meter of the components described In en 4.2.1 to 4.2.4. 4.2.1 4.2.2 Pressure foot, 20 mm + 2,5 mm square Indenter, the end being hemispherical, with a central hole of diameter between 2,0 mm and 3,0 mm. of diameter 1,55 mm to 1,60 mm. 4.2.3 Indicating device, allowing the extent of protrusion of the indentor beyond the face of the pressure foot to be read; the device shall be calibrated directly in terms of IRHD from 30° for maximum protrusion of 1,65 mm to 100° for nil protrusion obtained by placing the pressure foot and indentor in firm contact with a flat piece of glass. Calibrated spring, for applying 30 IRHD to 100 IRHD range. a substantially constant force to the indentor of 2,65 N t 0,15 N over the 4.2.4 5 5.1 Test piece of hardness by pocket hardness meters, the thickness of the piece shall be at least For the determination 6 mm. For sheets thinner than 6 mm, a test piece may be composed of not more than three layers, none of which shall be thinner than 2 mm, to obtain the necessary thickness, but determinations made on such test pieces may not agree with those made on single-thickness pieces. For comparison purposes, the test pieces shall be similar, 5.2 The other dimensions of the test piece shall be sufficient to permit measurements at least 12 mm away from any edge. The surface of the test piece shall be flat over the area in contact with the pressure foot. Satisfactory hardness determinations cannot be made on rounded, uneven or rough surfaces using pocket meters. However, their use in certain specialized applications is recognized, e.g. for determination of hardness of rubbercovered rolls. In such applications, the limitations of their use shall be clearly identified. 6 Conditioning Where practical, test pieces shall be conditioned immediately before testing for a minimum period of 1 h at the standard temperature in accordance with ISO 471. The same temperature shall be used throughout any one test or series of tests intended to be comparable. 7 7.1 Procedure Place the test piece on a hard, rigid surface. Hold the hardness meter in position with the centre of the indentor at least 12 mm from the edges of the test piece. Apply the pressure foot to the test piece as rapidly as possible, without shock, keeping the foot parallel to the surface of the test piece and ensuring that the indentor is nornlal to the rubber surface. Apply just sufficient force specified, take the reading after another time-lntewal position and pressure and to obtain firm contact between the pressure foot and the test piece. Unless otherwise within 1 s after the pressure foot is in firm contact with the test piece. When a reading is specified, hold the pressure foot in contact with the test piece without change in take the reading after the specified time. 4 IS 3400 ( Part 23 ) :2002 ISO 7619: 1997 7.2 Make five measurements determine the mean value. of hardness at different positions on the test piece at least 6 mm aparf and 7.3 When using Shore-type durometers, it is recommended that measurements be made with the type D instrument when values above 90 are obtained with the type A durometer, and that measurements be made with the type A instrument when values less than 20 are obtained with type D durometers. Values below 10 on the type A apparatus are inexact and should not be reported. NOTE 2 Better precision may be obtained by using either a stand or a weight centred on the axis of the indentor, apply the pressure foot to the test piece. For Shore-type durometers, masses of 1 kg and 5 kg are recommended and type D respectively. or both, to for type A 8 8.1 The Calibration Shore-type durometers spring of the durometer shall be calibrated by supporting the durometer in a vertical position and resting the point of the indentor on a small spacer at the centre of one pan of a balance, as shown in figure 3, in order to prevent interference between the pressure foot and the pan. The spacer has a small cylindrical stem of height approximately 2,5 mm and diameter approximately 1,25 mm and is slightly cupped on top to accommodate the indentor point. The weight of the spacer shall be balanced by a weight on the opposite pan of the balance. Weights shall be added to the opposite pan to balance the force on the indentor at various scale readings. The measured force shall be equal to the force calculated by the relevant equation given in 4.1.4. For type A instruments, the force shall be within * 80 mN of the calculated value and for type D instruments within t 440 mN. Alternatively, electronic balances or instruments specifically designed for calibration of durometers may be usbd.1 ) Balances or instruments used for calibration should be capable of measuring or applying force on the point of the indentor within 8,0 mN for the type A durometer and within 44,0 mN for the type D durometer. 8.2 8.2.1 IRHD pocket General hardness meter The instrument shall be calibrated and adjusted frequently, preferably against a range of standard rubber blocks that have been previously calibrated against a dead-load gauge by the method specified in ISO 48. Calibration of the instrument by mechanical means is recommended only where no suitable standard rubber test pieces are available. In such cases the manufacturer's instructions should be followed. 1) Instruments for the calibration of durometers are available from ShoreAVilson Hardness Testing Products, Instron Corporation, 02021-1089, USA; and Zwick GmbH & Co., Postfach 4350, D-7900 Ulm, Germany. 100 Royal Street, M/S Shore, Canton, MA 5 IS ISO 3400 ( Part 23 ) :2002 7619:1997 / !1 I I 1 Figure 3 -- Apparatus for calibration of durometer spring 8.2.2 Calibration using standard rubber blocksz) Press the instrument against a flat piece of glass and adjust the reading on the scale to give 100 IRHD. Using a set of standard rubber blocks covering the range approximately 30 IRHD to 90 IRHD, calibrate the instrument. All adjustments shall be made according to the manufacturer's instructions. The set of standard rubber blocks shall consist of at least six test pieces kept lightly dusted with talc in a suitable covered container away from light, heat, oil and grease. The standard rubber blocks shall themselves be calibrated against the dead-load gauge by the method specified in ISO 48 at intervals not exceeding 6 months. It is recommended blocks. that instruments in regular use be recalibrated at least each week against the standard rubber 9 9.1 Precision General repeatability and reproducibility were performed according to The precision calculations to express lSO/lR 9272:1986, Rubber and rubber products -- Determination of precision for test method standards. Consult this for precision concepts and nomenclature. Annex A gives guidance on the use of repeatability and reproducibility. 9.2 Precision details 9.2.1 An interlaboratory test programme (ITP) was organized and conducted by Statens Provningsanstalt (Sweden) in late 1985. Cured test pieces of four rubber compounds (materials) were prepared in one laboratory and sent to all participants. The nominal hardness values were 30, 45, 65 and 85. Thirty-two laboratories participated for measurement of the Shore meter hardness. On each of 2 days, 1 week apart, five determinations (measurements) of hardness were made on each compound. The median of the five values was used as a "test result" for the precision analysis. 2) Standard rubber blocks are available from Rapra Technology Ltd., Shawbury, Shrewsbury, Shropshire SY44NR, UK. 6 IS 3400 ( Part 23 ) :2002 ISO 7619:1997 9.2.2 Only four laboratories participated precision yields only a rough approximation in tests with the lRHD-type pocket meter. This small database of repeatability and reproducibility, and is not included here. test pieces circulated) for 9.2.3 The precision assessment is a type 1 (cured prepared and reproducibility is on a scale of days. and the time for repeatability 9.3 Precision results The precision as follows: r = results for the Shore hardness meter are given in table 1. The symbols used in this table are defined repeatability, in measurement units, (r) R = repeatability, = reproducibility, in percent (relative), in measurement units, (R) = reproducibility, in percent (relative). Table 1 -- Type 1 precision for a Shore hardness meter Within-laboratory repeatability Material A B c D Pooled values Interlaboratory reproducibility R (R) Average value r (r) 32,7 47,2 65,6 80,2 56,2 2,67 1,65 1,53 1,64 1,93 8,15 3,49 2,34 2,04 3,42 6,41 4,80 2,83 5,19 5,03 19,6 10,2 4,31 6,46 8,94 10 Test report The test report shall include the following information: a) b) a reference to this International sample details: 1) 2) 3) a full description compound of the sample and its origin, if known, its thickness and, in the case of a composite test piece, the Standard; details and curing conditions, a description of the test piece, including number of layers; c) test details: 1) the temperature humidity, of test, and the relative humidity when the hardness of the material is dependent on the 2) 3) 4) 5) the type of instrument used, of the test piece and the measurement of hardness, the time which elapsed between the preparation any deviation from the standard procedure, details of procedure not specified influence on the results; in this International Standard, and any incidents likely to have had an 7 IS 3400 ( Part 23 ) :2002 ISO 7619:1997 d) test results: values of the indentation hardness and the time interval the individual different from 1 s (see note 3), plus the mean value and the maximum in IRHDs or in Shore A or Shore D units; after which each reading was taken, if and minimum values, expressed either e) the date of the test. NOTE 3 For Shore-type durometers, readings may be reported in the form A 45/1, where A is the type of durometer, 45 is the reading, and 1 the time, in seconds, between bringing the pressure foot in firm contact with the test piece and making the reading, or alternatively A 45 when the preferred time of recording of 1 s is being used. 8 IS 3400 ( Part 23 ) :2002 ISO 7619:1997 Annex A (informative) Guidance for using precision A.1 results a positive The general procedure for using precision results is as follows, with the symbol Ixl - X21designating difference in any two measurement values (i.e. without regard to sign). Enter the appropriate precision table (for whatever test parameter is being considered) at an average value (of the measured parameter) nearest to the "test" data average under consideration. This line will give the applicable r, (r), R or (R) for use in the decision process. A.2 A.3 A.3.1 With these r and (r) values, the following general repeatability statements maybe used to make decisions. For an absolute difference: The difference Ixl - ,r2\ between two test (value) averages, found on nommally identical material samples under normal and correct operation of the test procedure, will exceed the tabulated repeatability r on average not more than once in twenty cases. A.3.2 For a percentage difference between two test (value) averages: The percentage difference [1X1 -Xk `XN21X'00 of the between two test values, found on nominally identical material samples under normal and correct operation test procedure, will exceed the tabulated repeatability (r) on average not more than once in twenty cases. A.4 A.4.1 (value) With these f? and @) values, the following general reproducibility statements may be used to make decisions. For an absolute averages, found difference: in two laboratories samples, will exceed the tabulated The absolute difference lx, - X21 between two independently using normal and correct test procedures on nominally reproducibility R not more than once in twenty cases. measured test identical material A.4.2 For a percentage difference between two test (value) averages: The percentage difference kl -X41(X1 `XJ21X100 between two independently measured test (value) averages, found in two laboratories using normal and correct test procedures on nominally identical material samples, will exceed the tabulated reproducibility (R) not more than once in twenty cases. 9 Bureau of Indian Standards BIS is a statutory institution established harmonious development of the activities and attending to connected matters under the Bureau of hxfian Sfartdarck Act, 1986 to promote of standardization, marking and quality certification of goods in the country. Copyright BIS has the copyright of all its publications. No part of these form without the prior permission in writing of BIS. This does of implementing the standard, of necessary details, such designations. Enquiries relating to copyright be addressed to Review of Indian Standards Amendments are issued to standards as the need arises on the basis of comments. Standards are also reviewed periodically; a standard along with amendments is reaffirmed when such review indicates that no changes are needed; if the review indicates that changes are needed, it is taken up for revision. Users of Indian Standards should ascertain that they are in possession of the latest amendments or edition by referring to the latest issue of `BIS Catalogue' and `Standards: Monthly Additions'. This Indian Standard has been developed from Doc : No. PCD 13 (1789). publications may be reproduced in any not preclude the free use, in the course as symbols and sizes, type or grade the Director (Publications), BIS. Amendments Amend No. Issued Since Publication Date of Issue Text Affected BUREAU OF INDIAN STANDARDS Headquarters: Manak Bhavan, 9 Bahadur Shah Zafar Marg, New Delhi 110002 Telephones :3230131, 3233375, 3239402 Regional Offices : Central : Manak Bhavan, 9 Bahadur Shah Zafar Marg NEW DELHI 110002 : 1/14 C.I.T. Scheme Vll M, V. 1. P. Road, Kankurgachi KOLKATA 700054 : SCO 335-336, Sector 34-A, CHANDIGARH 160022 { Southern : C.I.T. Campus, IV Cross Road, CHENNAI 600113 3378499, { 3378626, Telegrams : Manaksanstha (Common to all offices) Telephone 3237617 3233841 3378561 3379120 603843 602025 { Eastern Northern 2541216,2541442 2542519,2541315 { { 8329295, 8327858 8327891,8327892 Western : Manakalaya, E9 MlDC, Marol, Andheri (East) MUMBAI 400093 Branches : AH MEDABAD. BANGALORE. BHOPAL. BHUBANESHWAR. COIMBATORE. FARIDABAD. GHAZIABAD. GUWAHATI. HYDERABAD. JAIPUR. KANPUR. LUCKNOW. NAGPUR. NALAGARH. PATNA. PUNE. RAJKOT. THIRUVANANTHAPURAM. Printed at Prabhal Offset press, New Deihi-2